The present invention relates to an image processing device, an endoscope system, an image processing method, a computer-readable storage device, and the like.
A noise reduction process (NR process) is roughly classified into a spatial-direction NR process that reduces noise within the processing target frame and a time-direction NR process that reduces noise using the processing target frame and the preceding frame.
The spatial-direction NR process has a tendency in which a high-frequency component of the image is attenuated, and the time-direction NR process has a tendency in which a residual image occurs when the object makes a motion. Therefore, it has been desired to implement a sophisticated NR process by adaptively selecting the spatial-direction NR process when the image is stationary.
JP-A-6-47036 discloses a technique that determines whether the state of the image is a stationary state or a moving state, and adaptively switches the NR process between the time-direction NR process and the spatial-direction NR process corresponding to the determination result. In JP-A-6-47036, the state of the image is determined to be the stationary state when the inter-frame difference value (i.e., a difference value calculated between frames) is smaller than a threshold value, and determined to be the moving state when the inter-frame difference value is larger than the threshold value.